Method and machines for filling flexible tubular-bag packages

ABSTRACT

The invention relates to a tubular-bag machine and to a method for continuous or intermittent production of tubular-bag packages ( 02 ) which are filled with a product ( 03 ) in a tubular-bag machine ( 01 ) of this kind, the tubular-bag machine ( 01 ) comprising a screw-type metering device ( 10 ) in which a metering screw (OS) can be driven to rotate relative to a metering tube ( 06 ) for metering the product ( 03 ), and a compactor ( 07 ) by means of which the product ( 03 ) can be compacted by applying a vacuum and sucking out gas being provided ahead of, behind or within the metering tube ( 06 ), the compactor ( 07 ) comprising a suction bushing which is permeable to gas through fine pores and which extends coaxially with the metering tube ( 06 ), and at least part of the die suction bushing being surrounded by a vacuum chamber. By applying a vacuum, the pores of the suction bushing can be cleaned.

The invention relates to a method for continuous or intermittentproduction of tubular-bag packages using a tubular-bag machine accordingto the preamble of claim 1. Furthermore, the invention relates to atubular-bag machine for carrying out the method.

In known tubular-bag machines, a plurality of different products ispackaged into tubular-bag packages. These products can be powders orgranulates. It is often desirable, in particular in the case of grainyor fine-grained products, for the gas contained in the product, such asair or inert gas, to be extracted from the product during processing onthe tubular-bag machine so as to compact the product. Compacting of thiskind is often very important at the outlet of the metering tube, inparticular, in order to prevent undesired trickling of the product,which might otherwise end up in the fusion zone of the tubular bags tobe sealed. In principle, the compactor generically provided in thetubular-bag machine for compacting the product by extracting gas can beemployed anywhere in the metering tube. The compactor can be disposedahead of or behind the metering tube. It is also conceivable for thecompactor to be disposed within the extension of the metering tube, suchas in the middle of the metering tube.

Tubular-bag machines comprising generic compactors are known from DE 3915 144 A1 and from EP 1 033 332 A2, for example. These compactorscomprise a suction bushing permeable to gas through fine pores, theproduct to be degassed being led past the inside of the suction bushing.The suction bushing itself is surrounded at its outside by a vacuumchamber which can be subjected to a vacuum via a corresponding pressuresupply. Once the vacuum chamber has been subjected to the vacuum, thegas is sucked into the vacuum chamber from the outside through thepores, whereby the product led past the suction bushing is degassed. Thepores of the suction bushing need to have a pore width that is smallerthan the average particle size of the product in order to prevent theproduct particles from being sucked into the vacuum chamber.

When the known tubular-bag machines are being operated to producetubular-bag packages, cyclically repeating work cycles are run. Duringeach work cycle, one tubular bag is filled and closed by the sealingjaws.

One problem of the known vacuum compactors of generic tubular-bagmachines is that the suction bushings become increasingly blocked aftera certain operating time. Said blockage of the suction bushings iscaused by product particles depositing within the pores of the suctionbushings and closing them entirely or at least partially. Withincreasing blockage of the suction bushing, the vacuum existing in thevacuum chamber can no longer be transferred through the pores of thesuction bushing, causing the degassing of the product to continuouslydecrease as the blockage of the suction bushing grows. The growingblockage of the suction bushing can in particular also cause thecompaction of the product by gas extraction to become more irregular.Said irregularity is undesirable because it leads to greater meteringtolerances regarding the amount of product to be metered per package.

In order to still achieve the desired compaction of the product, generictubular-bag machines require removal and cleaning of the suction bushingby operating personnel at specific maintenance intervals. However, suchcleaning of the suction bushing means a significant amount ofinstallation work. Also, the tubular-bag machine cannot be used toproduce tubular tabs as long as the suction bushing is removed, which iswhy the necessary cleaning of the suction bushings causes undesirabledowntimes.

Therefore, the object of the present invention is to propose a newmethod for continuous or intermittent production of tubular-bag packagesusing a tubular-bag machine by means of which the amount of work forcleaning the blocked compactor is reduced and downtimes are avoided.Furthermore, compaction of the product is to be kept within freelyadjustable limits so as to achieve high metering accuracy and processreliability of the metering process, resulting in economic advantages.Furthermore, the object of the invention is to propose a tubular-bagmachine for carrying out the method.

These objects are attained by a method and by a tubular-bag machineaccording to the teaching of the independent main claims.

Advantageous embodiments of the invention are the subject-matter of thedependent claims.

In the method according to the invention, during the tubular-bagproduction process with its cyclically repeating work cycles forproducing one tubular bag each, a suctioning phase is performed duringthe work cycle in the known manner. During said suctioning phase, avacuum is established in the vacuum chamber in the known way so as tocompact the product by sucking gas out through the pores of the suctionbushing. The vacuum in the vacuum chamber can be lifted to ambientpressure between the individual suctioning phases. However, it is alsoconceivable for the suctioning phases associated with the individualwork cycles to seamlessly transition into each other for some time. Thismeans that the vacuum in the vacuum chamber stays the same for multiplework cycles, whereby a permanent compaction during these work cycles isrealized.

The gas may usually be air. However, if the tubular-bag machine isoperated under inert gas in order to prevent oxidation processes in theproduct, the gas can of course also be a corresponding inert gas.

The basic idea of the method according to the invention is that thepores of the suction bushing are cleaned during the tubular-bagproduction process with its cyclically repeating work cycles so as toavoid downtimes as those caused by interruption of the tubular-bagproduction process. The actual cleaning of the pores of the suctionbushing is effected by integration of a blowing phase, during which thevacuum chamber is pressurized, in at least one work cycle. The pressurein the vacuum chamber during the blowing phase causes the gas to flow inthe opposite direction from the vacuum chamber through the pores of thesuction bushing in the direction of the product, at least some of theproduct particles stuck in the pores thus being removed. By this way ofcleaning the suction bushing by blowing in a blowing phase being part ofat least one work cycle of the tubular-bag production process, downtimesare reduced or even avoided entirely because the cleaning required toprevent blockage of the suction bushing is carried out during the actualtubular-bag production process. The length and intensity of the cleaningby blowing the pores of the suction bushing is to be selected in such away that, on the one hand, a sufficient cleaning effect is achieved and,on the other hand, there remains enough process time for carrying outthe compacting in the suctioning phases.

The intervals at which the blowing phases according to the invention forcleaning the suction bushing are executed during the tubular-bagproduction process are generally optional as long as a sufficientcleaning effect is achieved. In particular, this is because thefrequency of the blowing phases depends on the particular product to bepackaged since powdery products, in particular, have a stronger tendencyto block the pores of the suction bushing. A particularly simplestrategy for cleaning the suction bushing intends for the blowing phasesto be executed after a regular number of work cycles in each case. Forexample, it may be intended that after each three, five or ten tubularbags, a short blowing phase is executed in the respective next workcycle in order for the particles that have accumulated in the pores inthe previous work cycles and now adhere to the insides of the pores tobe blown out again. In the case of products with a strong tendency tocause blockage, it may also be intended for a short blowing phase to bepart of each work cycle, a suctioning phase and a blowing phase thusbeing run during each work cycle in this case.

Alternatively or additionally to the strategy of executing the blowingphases as a function of the work cycles, the suction bushing can also beblown as a function of the process time for which the suction bushinghas been used in compacting the product. For example, it is conceivablethat the suction bushing is cleaned by blowing at regular intervals of,for example, three, five or ten minutes during the work cycle thatfollows next in each case.

If the blowing phases are executed as a function of the work cycles andof the process time, the number of work cycles and the duration of theprocess time before execution of the next blowing phase, respectively,have to be set by operating personnel. Said setting will be made basedon operating personnel's experience as to how heavily the suctionbushing becomes blocked during processing of a particular product.Naturally, mistakes can happen in this process, which may cause thenumber of blowing phases to be too small to ensure sufficient cleaningof the suction bushing. Hence, in order to avoid such mistakes, it isparticularly advantageous if the effective vacuum during the suctioningphases is measured using a pressure sensor. This is advantageous becausethe degree of blockage of the suction bushing can be assessed based onthese measured vacuum values and the manner of cleaning by blowing thesuction bushing can be varied as a function of the measured values.

It is advantageous, in particular, if the process parameters for blowingthe suction bushing are changed as a function of the vacuum valuesmeasured using the pressure sensor. For instance, the duration of theindividual blowing phases can be varied as a function of the measuredvacuum values so as to clean the suction bushing more thoroughly bylonger blowing phases if the vacuum values deteriorate, for example.

Alternatively or additionally, the pressure level in the blowing phasescan be changed as a function of the vacuum values measured using thepressure sensor. By increasing the pressure level during the blowingphases, a stronger cleaning effect is achieved. So if the measuredvacuum values indicate growing blockage of the suction bushing, cleaningof the pores in the suction bushing can be intensified by increasing thepressure level.

If the vacuum in the vacuum chamber is measured during the suctioningphases, in particular the time between the individual blowing phases canbe varied as a function of the measured vacuum values. For example, ifthe vacuum values indicate growing blockage of the pores in the suctionbushing, the frequency of the blowing phase can be increased. At thebeginning of the tubular-bag production process where the pores in thesuction bushing are not blocked, the process can start with a blowingphase frequency at which the pores of the suction bushing are cleaned byblowing only every ten work cycles, for example. Then, if blockage ofthe pores in the suction bushing grows during the continuing tubular-bagproduction process, the blowing phase frequency can be increased inincrements so that a blowing phase may be executed every nine, thenevery eight, then every seven, then every six, then every five, thenevery four, then every three, then every two work cycles and, finally,at the end of each work cycle.

Depending on the particular product to be packaged, it can of coursehappen that at some point the cleaning effect that can be achieved byblowing the suction bushing does no longer suffice to ensure that thepores of the suction bushing remain appropriately unobstructed. So ifall options for increasing the cleaning effect, such as increasing theblowing phase frequency or increasing the duration of the individualblowing phases or increasing the pressure level in the blowing phases,have been exhausted and the vacuum during the vacuum phases still doesnot reach a certain level, the tubular-bag production process should beinterrupted because reliable operation of the tubular-bag machine is nolonger ensured given the insufficient vacuum level. Hence, it isintended according to a preferred version of the method for a limitvalue that the measured vacuum must not fall short of is stored in thecontroller of the tubular-bag machine. If the limit value is no longerreached during the tubular-bag production process in this case, thetubular-bag production process is interrupted or an error is reported.

The limit value for the vacuum during the suctioning phases depends notonly on the degree to which the pores in the suction bushing are cleanedbut also on the particular product to be packaged, which means that saidlimit value has to be defined specifically for each product. Tofacilitate said product-specific definition of the limit value to beobserved, a preferred version of the method intends for the effectivevacuum during a suctioning phase using a cleaned suction bushing to bemeasured using the pressure sensor and to be stored as an initial vacuumvalue. Said initial vacuum value represents the margins cleared when thesuction bushing is clean and the maximum vacuum that can be achievedwhen the particular product is being packaged. The limit value forinterruption of the tubular-bag production process or for reporting anerror can then be determined as a function of said measured initialvacuum value. For example, it may be defined that the limit value is10%, 20%, 30%, 40% or 50% below the initial vacuum value. If themeasured vacuum falls short of said threshold derived from the initialvacuum value, i.e. if the measured vacuum value is 10%, 20%, 30%, 40% or50% below the initial vacuum value, the tubular-bag production processis interrupted or an error is reported so as to allow operatingpersonnel to take suitable countermeasures, such as removal and cleaningof the suction bushing or replacing the blocked suction bushing with anew suction bushing.

The tubular-bag machine according to the invention has a conventionalstructure including a screw-type metering device and, provided thereon,a compactor having a suction bushing. To allow the method according tothe invention to be carried out, it is intended for the vacuum chamberof the tubular-bag machine according to the invention to be connectablenot only to a vacuum source as is the case in the state of the art but,according to the invention, also to a pressure source. The compactorwill be controlled by the controller as a function of the processparameters of the tubular-bag production process in such a manner that,as a function of the process, blowing phases in which the vacuum chamberis subjected to pressure from the pressure source are executed. Thepressure during the blowing phases causes the pores of the suctionbushing to be cleaned by blowing out product particles that adhere tothe insides of the pores. Cleaning of the pores of the suction bushingtakes place during the tubular-bag production process, thus avoidingdowntimes for this manner of cleaning.

In order to be able to execute the blowing phases to be executedprocess-dependently during the tubular-bag production as a function ofthe blockage present in each of the pores of the suction bushing, it isparticularly advantageous if a pressure sensor by means of which theeffective vacuum in the vacuum chamber and/or in the vacuum lines can bemeasured is provided on the tubular-bag machine. In this way, theprocess parameters of the blowing process can be varied as a function ofthe measured vacuum, which provides information as to the blockage ofthe pores of the suction bushing.

The architecture of the screw-type metering device of the tubular-bagmachine is basically optional. In a particularly preferred case, thescrew-type metering device can be a filling metering screw which isdisposed immediately above the sealing jaws which are provided forsealing the tubular bags. Compactors working with vacuum are widely usedwith these filling metering screws because they allow reliableprevention of trickling of the product into the fusion zone of thesealing jaws located below.

Alternatively, the screw-type metering device can also be configured inthe manner of a feeding screw which is disposed in front of a storagetank for intermediate storage of the product.

Different embodiments of the invention are schematically illustrated inthe drawing and will be explained below by way of example.

FIG. 1 shows a side view of a schematically illustrated tubular-bagmachine having a compactor;

FIG. 2 shows a cross-section of the compactor of the tubular-bag machineof FIG. 1;

FIG. 3 shows a perspective side view of the compactor of FIG. 2;

FIG. 4 shows a time diagram of the process parameters of a first methodfor cleaning the compactor of FIG. 2;

FIG. 5 shows a time diagram of the process parameters of a second methodfor cleaning the compactor of FIG. 2;

FIG. 6 shows a time diagram of the process parameters of a third methodfor cleaning the compactor of FIG. 2;

FIG. 7 shows a time diagram of the process parameters of a fourth methodfor cleaning the compactor of FIG. 2.

FIG. 1 shows a schematic side view of a tubular-bag machine 01 forproducing tubular-bag packages 02. In FIG. 1, the tubular-bag machine 01is illustrated only with the components that are necessary forunderstanding the invention. For filling the tubular-bag packages 02with the grainy or fine-grained product 03, the latter is first fed intoa storage tank 04 and then fed in metered amounts from the storage tank04 into the tubular-bag packages 02 by a metering screw 05 being drivento rotate. A compactor 07 by means of which air or inert gas can besucked from the product to be discharged at the end of the metering tube06 is located at the lower end of the metering tube 06. Sucking the airor inert gas from the product at the end of the metering tube 06prevents the product from trickling in an uncontrolled manner into thespace between the sealing jaws 08 by means of which the tubular-bagpackages 02 are sealed. The drive 09, the storage tank 04, the meteringscrew 05 and the metering tube 06 form the main components of themetering device 10 in the tubular-bag machine 01.

The compactor 07 can be selectively connected to a pressure source 11and to a vacuum source 12. A switching valve 13 controlled by acontroller 14 is provided for switching between the pressure source 11and the vacuum source 12. The controller 14 for controlling the pressuresupply at the compactor 07 can of course also be integrated in the maincontroller of the tubular-bag machine 01.

At the compactor 07, there is a pressure sensor 15 by means of which thevacuum effective at the compactor 07 during operation of the compactor07 can be measured. The pressure sensor can alternatively also bedisposed on one of the pressure lines. The data of the pressure sensor15 is transmitted to the controller 14 via a data line. Also, thecontroller 14 is connected to the drive 09 via a data line. In this way,the operating state can be transmitted to the controller 14 as themetering screw 05 is being driven. The pressure from the pressure source11 and the vacuum from the vacuum source 12 are transferred to thecompactor 07 via a pressure line 16 starting from the switching valve13.

FIG. 2 shows the compactor 07 including the pressure sensor 15 and thepressure line 16 in an enlarged sectional view. The compactor 07 islocated at the lower end of the metering tube 06, in which the meteringscrew 05 for metering the products 03 can be driven to rotate. In FIG.2, the metering tube 06 is illustrated in the unfilled state in order tofacilitate understanding of the compacting device 07.

In the compactor 07, a suction bushing 17 for sucking gas from theproduct to be conveyed by the metering screw 05 is provided. The suctionbushing 17 is composed of a perforated support plate 18 on which thefine-pored filter mat 19 rests. At its outside, the suction bushing 17is surrounded by a vacuum chamber 20 which can be selectively subjectedto pressure or to vacuum via the pressure line 16. When the vacuumchamber 20 is subjected to a vacuum, the gas is sucked out of theproduct conveyed by the screw 05 through the pores of the filter mat 19into the vacuum chamber 20, whereby the product is compacted in thedesired manner. If the vacuum chamber 20 is then subjected to pressurein another work cycle, the gas flows in the opposite direction throughthe pores of the filter mat 19, the product particles adhering to theinside of the pores thus being blown out. In this way, the desiredcleaning effect for cleaning the suction bushing 17 is achieved.

FIG. 3 shows the lower end of the suction tube 06, the metering screw05, the compactor 07 including the pressure sensor 15 and the pressureline 16, and a product die 21 in a combined perspective illustration.

In a time diagram, FIG. 4 shows a first method for cleaning thecompactor 07 by blowing as per the invention. FIG. 4 illustrates theflow of a tubular-bag production process in a window of three workcycles, the individual work cycles being separated from each other bydashed vertical lines. In the upper part of FIG. 4, the speed ofrotation of the metering screw 05 during the individual work cycles ismarked out. As is visible, the metering screw stands still up to time t1and is then driven at a constant speed of rotation by the drive 09 for apredefined process time so as to feed a specific amount of the product03 into a tubular bag 02. At time t2, the speed of rotation of themetering screw 05 is reset to zero.

In the lower part of FIG. 4, the pressure to which the vacuum chamber 20is pressurized via the pressure line 16 is marked out. In the diagram,vacuums P− are marked out upward and pressures P+ are marked outdownward. As is visible, a vacuum from the vacuum source 12 isestablished in the vacuum chamber 20 via the pressure line 16 duringevery single work cycle at time t1 synchronously to the rotation of themetering screw 05 so as to suck gas from the product 03 waiting in themetering tube during the thus defined suctioning phases 29. The vacuumis maintained starting at time t1 until time t3 within the suctioningphases 29 during each work cycle. Time t3 occurs shortly after theswitch-off time t2 of the metering screw in order to ensure, bycorresponding compacting of the product even after the metering screw 05has been switched off, that the product 03 does not drop out of themetering tube 06 into the fusion zone between the sealing jaws 08.

The version of the method illustrated in FIG. 4 intends for the pores inthe filter mat 19 to be cleaned in every third work cycle during ablowing phase 28. Hence, at time t4 of each third work cycle, theswitching valve 13 is switched and the vacuum chamber 20 is thensubjected to pressure from the pressure source 11 via the pressure line16. The pressure impulse ends at time t5 shortly prior to the start ofthe respective fourth work cycle. The pressure impulse briefly blows thepores in the filter mat 19 of the suction bushing 17 and blows theproduct particles stuck therein back into the direction of the meteringscrew 05. Since cleaning of the suction bushing 17 in the compactor 07takes place during the tubular-bag production process, namely in eachthird work cycle, the cleaning work on the compactor 07 that wouldotherwise have to be performed regularly and which causes undesireddowntimes can be significantly reduced or even avoided entirely.

FIG. 5 shows an alternative version of the method in a time diagram inwhich the speed of rotation of the metering screw 05 is marked out inthe upper part and the pressure supply of the compactor 07 is marked outin the lower part. Contrary to the method illustrated in FIG. 4,cleaning of the suction bushing 17 takes place by way of blowing phases28 during every single work cycle in the method illustrated in FIG. 5.The pressure supply is switched to pressure at time t6 during everysingle work cycle, whereby the pores in the filter mat 19 are blown.Then, at time t7 shortly prior to the end of the respective work cycle,the pressure supply is reset to zero.

In FIG. 6, the time diagram of another version of the method forcleaning the compactor 07 by blowing the pores in the filter mat 19during the tubular-bag production process is schematically illustrated.The individual work cycles of the tubular-bag production process areagain separated from each other by dashed vertical lines. As in thepreviously explained method according to FIG. 4 and FIG. 5, the vacuumchamber 20 is again subjected to the vacuum from the vacuum source 12between times t1 and t3 during every single work cycle. In the firstwork cycle at the beginning of the tubular-bag production process, theeffective vacuum in the vacuum chamber during application of the vacuumfrom the vacuum source 12 is measured using the pressure sensor 15. Saideffective vacuum in the vacuum chamber 20 during the first work cycle isstored as an initial vacuum value 22. Since the pores of the suctionbushing 17 are not yet blocked at the beginning of the tubular-bagproduction process, the initial vacuum value 22 is below the vacuumlevel from the vacuum source 12.

A limit value 23 which serves to trigger cleaning of the compactor 07 byblowing the pores in the suction bushing 17 is determined based on themeasured initial vacuum value 22. The limit value 23 can be double theinitial vacuum value 22, for example.

On the right side of FIG. 6, two work cycles of the tubular-bagproduction process at a later time, such as after running of severalhundred work cycles, are marked out. As is visible, the vacuum value 24measured using the pressure sensor 15 has largely approached the limitvalue 23 because of the growing blockage of the pores in the suctionbushing 17. If the vacuum value 25 now exceeds the limit value 23 in thenext work cycle, this will cause the controller 14 to automaticallytrigger a blowing phase 26 in which the vacuum chamber 20 is subjectedto pressure from the pressure source 11 during times t8 and t9 so as toblow the pores of the suction bushing 17.

In FIG. 7, the process parameters of another version of the method forcleaning the compactor of FIG. 2 are presented in a time diagram. Thisversion of the method largely corresponds to the version of the methodillustrated in FIG. 6. However, this version of the method intends forthe blowing phases 30 to seamlessly transition into each other startingfrom initial time t10 of the first work cycle. Again, the limit value 23serving to trigger cleaning of the compactor 07 by blowing the pores inthe suction bushing 17 is determined based on the measured initialvacuum value 22.

In the 40^(th) work cycle, for example, the measured vacuum pressure 31is just barely below the limit value 23. In the subsequent 41^(st) workcycle, the measured vacuum value 32 is then just above the limit value23, which causes the controller to trigger a cleaning cycle including ablowing phase 33 so as to clean the pores by blowing out depositedparticles. After that, starting with the next work cycle, the vacuumchamber is permanently subjected to a vacuum again so as to compact theproduct by sucking out gas. Once the measured vacuum value exceeds thelimit value 23 again, another cleaning cycle including a blowing phase33 will be triggered.

1. A method for continuous or intermittent production of tubular-bagpackages (02) which are filled with a product (03) in a tubular-bagmachine (01), the tubular-bag machine (01) comprising a screw-typemetering device (10) in which a metering screw (05) can be driven torotate relative to a metering tube (06) for metering the product (03),and a compactor (07) by means of which the product (03) can be compactedby applying a vacuum and by sucking out gas being disposed ahead of,behind or within the metering tube (06), the compactor (07) comprising asuction bushing (17) which is preamble to gas through fine pores andwhich extends coaxially with the metering tube (06), and at least partof the suction bushing (17) being surrounded by a vacuum chamber (20),the method comprising the following method steps, which are to beexecuted during a tubular-bag production process including multiplecyclically repeating work cycles: establishing a vacuum in the vacuumchamber (20) in a suctioning phase (27, 29, 30) during at least one workcycle in order to compact the product (03) by sucking out gas,establishing pressure in the vacuum chamber (20) in a blowing phase (26,28, 33) during at least one work cycle in order to clean the pores ofthe suction bushing (17) by blowing out product particles that adhere tothe inside of the pores during the tubular-bag production process. 2.The method according to claim 1, characterized in that the blowingphases (28, 33) are each executed after a regular number of work cycles,in particular during each work cycle.
 3. The method according to claim1, characterized in that the blowing phases are each executed afterlapse of a predefined process time.
 4. The method according to claim 1,characterized in that the effective vacuum during the suctioning phases(27, 29, 30) is measured using a pressure sensor (15).
 5. The methodaccording to claim 4, characterized in that the process parametersduring blowing of the suction bushing (17) are changed during theblowing phases (26, 28, 33) as a function of vacuum values measuredusing the pressure sensor (15).
 6. The method according to claim 5,characterized in that the duration of the blowing phases (26, 28) ischanged as a function of the vacuum values measured using the pressuresensor (15).
 7. The method according to claim 5, characterized in thatthe pressure level in the blowing phases is changed as a function of thevacuum values measured using the pressure sensor (15).
 8. The methodaccording to claim 5, characterized in that the blowing phases (26) aretriggered as a function of a vacuum value (25) measured using thepressure sensor (15).
 9. The method according to claim 8, characterizedin that the effective vacuum during a suctioning phase executed using acleaned suction bushing is measured using a pressure sensor and isstored as an initial vacuum value (22), a limit value (23) fortriggering the blowing phases being determined as a function of theinitial vacuum value.
 10. The method according to claim 1, characterizedin that the tubular-bag production process is interrupted or an error isreported if the vacuum pressure during the suctioning phases (27, 29,30) measured using the pressure sensor (15) exceeds a predefined limitvalue (30).
 11. A tubular-bag machine (01) for continuous orintermittent production of tubular-bag packages (02) which are filledwith a product (03), comprising a metering device (10) in which ametering screw (05) can be driven to rotate relative to a metering tube(06) for metering the product (03), a compactor (07) by means of whichthe product (03) can be compacted by applying a vacuum and by suckingout gas being provided ahead of, behind or within the metering tube(06), and the compactor (07) comprising a suction bushing (17) which ispermeable to gas through fine pores and which extends coaxially with themetering tube (06), and at least part of the suction bushing (17) beingsurrounded by a vacuum chamber (20), and the vacuum chamber (20) beingconnectable to a vacuum source (12), and the compactor (07) beingcontrolled by a controller (14) as a function of the tubular-bagproduction process (14) so as to establish a vacuum in the vacuumchamber (20) in suctioning phases (27, 29, 30) as a function of theprocess and to compact the product (03) by sucking out gas,characterized in that the vacuum chamber (20) can selectively also beconnected to a pressure source (11), the compactor (07) being controlledby the controller (14) as a function of the tubular-bag productionprocess so as to establish a vacuum in the vacuum chamber (20) inblowing phases (26, 28, 33) as a function of the process, the pores ofthe suction bushing (17) being cleanable during the blowing phases (26,28, 33) by blowing out product particles that adhere to the inside ofthe pores during the tubular-bag production process.
 12. The tubular-bagmachine according to claim 11, characterized in that the effectivevacuum in the vacuum chamber (20) and/or in the vacuum lines (16) can bemeasured using a pressure sensor (15).
 13. The tubular-bag machineaccording to claim 11, characterized in that the metering device (10)comprises a metering screw (05) with an associated metering tube (06)which are disposed immediately above the sealing jaws (08) for sealingthe tubular-bag packages (03).
 14. The tubular-bag machine according toclaim 11, characterized in that the screw-type metering device isconfigured in the manner of a feeding screw which is disposed in frontof a storage tank (04) for intermediate storage of the product.